content: /*
   * Copyright 2017 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.reactive4javaflow.impl.consumers;
  
  import hu.akarnokd.reactive4javaflow.FolyamSubscriber;
  import hu.akarnokd.reactive4javaflow.impl.*;
  
  import java.lang.invoke.*;
  import java.util.concurrent.*;
  
  public final class CompletionStageConsumer<T> extends CompletableFuture<T> implements FolyamSubscriber<T> {
  
      T item;
  
      Flow.Subscription upstream;
      static final VarHandle UPSTREAM = VH.find(MethodHandles.lookup(), CompletionStageConsumer.class, "upstream", Flow.Subscription.class);
  
      @Override
      public void onSubscribe(Flow.Subscription subscription) {
          if (SubscriptionHelper.replace(this, UPSTREAM, subscription)) {
              whenComplete(this::cancel);
              subscription.request(Long.MAX_VALUE);
          }
      }
  
      void cancel(T t, Throwable e) {
          SubscriptionHelper.cancel(this, UPSTREAM);
          item = null;
      }
  
      @Override
      public void onNext(T item) {
          this.item = item;
      }
  
      @Override
      public void onError(Throwable throwable) {
          item = null;
          super.completeExceptionally(throwable);
      }
  
      @Override
      public void onComplete() {
          super.complete(item);
      }
  }
  